The American Academy of Pediatrics, American Heart Association, Centers for Disease Control and Prevention, Institute of Medicine, and the World Health Organization have all recognized the deleterious effects of sedentary behavior (SB) in youth. Sedentary is defined as behaviors that do not sufficiently raise resting energy expenditure, with metabolic equivalents of 1.0-1.5 and accelerometry values of less than 100 counts per minute. Youth are active persons that favor short bursts of behaviors. SB is implicated in the development of obesity. Current research estimates that nearly one third of all youth are overweight (e85th percentile) and 16.9% are obese (e95% percentile). SB and weight disturbances are linked with early morbidity and death. Appallingly, the current generation may have a shorter life expectancy than their parents. The NINR Director has specifically mentioned that fresh solutions need to be found in areas of SB and obesity. Older adolescents in particular have the largest increase in SB and obesity, and the greatest decrease in physical activity over the last few decades compared to other groups. Valid and reliable measures of SB will strengthen future descriptive studies from which fresh solutions and nursing interventions will be developed. The proposed pilot study specifically aims to: 1) validate the inclinometry function to measure SB in older adolescents (18- to 19-year-olds), and, 2) develop an innovative algorithm, the Sedentary Outcome Score (SOS), using the longest average daily sedentary episode and average total daily sedentary time and correlating these with body mass index (BMI) percentile and waist circumference. The proposed study seeks to validate inclinometry in older adolescents and applies a novel method, using both accelerometry and inclinometry data, to measure SB. Just as total sedentary time is associated with obesity and other negative health outcomes; individual sedentary episode length is independently associated with increased morbidities. The proposed study builds on this evidence and advances it using an innovative approach by linking the health indicators of BMI and waist circumference with the proposed SOS. Although total sedentary time and sedentary episodes are significantly correlated with BMI and waist circumference in youth, this correlation is low to moderate in strength. An algorithm combining the two to improve the strength of the association has yet to be explored and would be valuable given that few objective measures specific to SB exist in the literature. Results of this study have the potential to advance how SB is understood and measured in youth, impacting future interventions in this emerging field.